Environmental Flow Components Research Articles

Multicriteria decision analysis framework for hydrological decision support using environmental flow components

Assessing the quantity and quality of water available in water stressed environments under various potential climate and land-use changes is necessary for good water and environmental resources management and governance. We present a novel approach with which to assess water quantity in the Luanginga basin, a subbasin of the upper Zambezi River, using existing results of hydrological modelling based on climate change scenarios, hydrological indicators, and multicriteria decision analysis. Flexible input criteria and open-source software are used to the greatest degree possible. Scenarios are represented through a combination of model input data and parameter settings in the hydrological model, and preferences are represented through criteria weighting in the multicriteria decision analysis. The resulting methodology, combining hydrological indicators with MCDA, is thus adaptable, in terms of both application platform and subject matter. The method results were largely as expected. When a decision maker expressed a preference for wetter conditions, the RCP 4.5 scenarios were generally deemed most suitable, and thus ranked highest. When drier conditions where preferred, the RCP 8.5 scenarios, resulting in less streamflow and less frequent flood events, were ranked highest. Validation of the results is not possible, due to the methodologically exploratory nature of the research being undertaken. The promising results do, however, allow for further research that builds upon the work undertaken here, to be envisaged.

Applying the environmental flow components approach to the River Murray in South Australia

ABSTRACTRiver regulation has degraded the River Murray’s riverine ecosystems. Environmental flows are now being delivered to restore these ecosystems to a more natural, pre-regulation state. To guide the development of environmental flow recommendations, I calculated 28 Environmental Flow Components for the River Murray in South Australia, comparing simulated flow data for natural and present conditions. Regulation has caused complex changes to the rivers’ hydrology. Under present conditions, the inter-annual frequency of extreme low flows (<4150 ML/day) and high flow pulses (15,000–55,000 ML/day) has increased, whilst for small floods (55,000–100,000 ML/day) and large floods (>100,000 ML/day) frequency has declined. The magnitude of low flows (4150–15,000 ML/day) has been reduced for all months, and extreme low flows and high flow pulses occur later in the year. The duration of high flow pulses, and both small and large floods, have also declined under present conditions. Restoring more natural extreme low flows and high flow pulses will require new events to be engineered, whilst environmental water can be used to enhance monthly low flows and small floods. In addition to providing environmental flows, changes to river operations, particularly instituting weir pool manipulation, is required to maximise ecological outcomes.

Identifying hydrological regime and eco-flow threshold of small and medium flood of the Xiaoqing River in Jinan city

It was known that hydrological regime was the main influencing factor of river ecosystem, but the regime of different flow rates of urban rivers was poorly understood. We collected daily inflows at the Huangtai station of the Xiaoqing River from 1960 to 2014 and divided the data into three periods. Then we calculated hydrological parameters by the method of EFCs (Environmental Flow Components) and analyzed the tendency and change rates of each component respectively in the three periods. Combined with the ecological significance of environmental flow components, we identified the small and medium flood had the greatest impact on the river regime and ecosystem. And then we used the hydraulic parameters in the good ecosystem period as control conditions, to calculate the ecological threshold of the flow component under the current situation. This study could provide technical support for restoring and improving hydrological regime and ecological environment of the Xiaoqing River in Jinan city.

Effect of Hydrologic Alteration on the Community Succession of Macrophytes at Xiangyang Site, Hanjiang River, China.

With the intensification of human activities over the past three decades in China, adverse effects on river ecosystem become more serious especially in the Hanjiang River. Xiangyang site is an important spawn ground for four domestic fishes in the downstream region of Hanjiang River. Based on the field survey results of macrophytes during 1997–2000 and 2013-2014, community succession of aquatic macrophytes at Xiangyang site was evaluated and discussed. Two-key ecologic-related hydrologic characteristics, flow regime and water level, were identified as the main influence factors. The EFC (environmental flow components) parameters were adopted to evaluate the alteration of flow regimes at Xiangyang site during 1941–2013. Evaluation results demonstrate a highly altered flow process after being regulated by reservoir. The flow patterns tend to be an attenuation process with no large floods occurring but a higher monthly low flow. Furthermore, the water level decreased and fluctuation reduced after the dam was built, which caused the decrease of biomass but favored the submerged macrophytes during 1995–2009. However, with the water level increasing after 2010 and gently fluctuating, due to uplift by the hydraulic projects downstream as well as the flow attenuation, the dominant position of submerged macrophytes will be weakened.

Integrating Hydrological Modelling and Ecosystem Functioning for Environmental Flows in Climate Change Scenarios in the Zambezi River (Zambezi Region, Namibia)

AbstractThe Zambezi‐Chobe wetlands in Namibia are of great international importance for trans‐boundary water management because of their remarkable ecological characteristics and the variety and magnitude of the ecosystem services provided. The main objective of this study is to establish the hydro‐ecological baseline for the application of environmental flow regimes (EFR). The specific objectives are: (i) the assessment of environmental flow components (EFC) in the current near‐natural hydrological conditions; (ii) the generation of future scenarios for climatic and socioeconomic changes; (iii) the estimation of the area–duration curves and estimated annual habitat during the inundation of the critical habitats for fisheries (mulapos), under the existing conditions and future scenarios; and (iv) to provide a framework for the future application of EFRs, based on hydrological and ecological processes. To make a sound analysis of the ecological implications, first we develop a conceptual framework of the linkages between the hydrological and biological processes concerning fish communities, because of the critical role of fisheries in the region. The EFCs in near‐natural hydrological conditions provide the basis for developing interim EFRs in the region, within the framework of an adaptive management of water resources. The future scenarios indicate a mitigation of the flow variability; and, in the worst‐case scenario, the reduction of the maximum flow and inundated area of the mulapos would result in a reduction of the estimated annual habitat of 22%. This means a reduction in the spawning habitats for quiet‐water species, in the food resources for fry and juvenile fish and a consequent reduction in fish stocks. Furthermore, the habitat loss during low events is similar and greater under both scenarios, at ca. 35%. Here we corroborate that the EFCs and their variability may become the building blocks of flow‐ecology models that lead to environmental flow recommendations, monitoring and research programmes and flow protection activities. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Effect of Climate Change on Environmental Flow Components and Physical Habitats

The quantity and timing of runoff are critical components for the water supply, water quality, and ecological interaction of river systems (Poff, et al., 1997). Five components of the flow regime (magnitude, frequency, duration, timing, and rate of change) can directly and indirectly impact an aquatic ecosystem. (Karr, 1991; Poff, et al., 1997). Due to the recent phenomenon of climate change, the timing and pattern of rainfall has changed and affected the flow regime of certain basins. Hence, in this research, the future impact of climate change on the river flow regime and aquatic ecosystem of the Mangyeong River, a medium-sized basin in Korea, has been quantified by analysis of environmental flow components and physical habitat modeling. Consequently, it is predicted that there will be crucial changes in the material conditions related to the river flow regime, and the risk of ecological environmental changes will greatly increase. KeywordsClimate Change; EFCs; CSI; Environmental Flow Components

Recent changes (1973-2014 versus 1903-1972) in the flow regime of the Lower Paraná River and current fluvial pollution warnings in its Delta Biosphere Reserve.

Alterations in flow regimes of large rivers may originate or increase risks to ecosystems and humans. The Paraná River basin (South America) undergoes human pressures (e.g., heavy damming in the upper basin, deforestation, and mixed pollution) that may affect the water quantity and quality of its terminal Delta (Argentina). In this study, after applying univariate and multivariate change-point detection and trend analyses to the daily data series of flows incoming to the Delta (Paraná-Santa Fe section), flow characteristics were compared by Indicators of Hydrologic Alteration (IHA) and Environmental Flow Components (EFC). Some flood characteristics were also compared from hydrometric levels in the middle Delta (San Pedro station). Chemical and microbiological water variables in the main rivers of the "Paraná Delta" Biosphere Reserve were examined during two extreme hydrologic years (October 2008 to July 2010) to detect potential risk factors in association with hydrologic conditions. In the Lower Paraná River, a historical period (1903-1972) and two more altered periods (1973-1999wet period and 2000-2014dry period) were identified. Flow duration curves evidenced different changes in both altered periods, reflecting the joint effect of climatic variability and human influence. The most evident alterations in the flow regime were the lack of record of the extreme-low-flow component, the attenuation of monthly flow seasonality, and the increase in the number of reversals (dry period) and in the variability of maximum and minimum flow dates. These alterations are consistent with the monthly and daily flow regulation by upstream dams evidenced by available data from the current dry period. In the middle Delta, the marked monthly seasonality in flood days decreased only in the wet period. The proportion between the number of flood days exceeding the evacuation level and that of those exceeding the warning level doubled in the wet period but decreased only slightly in the dry period. In the Delta Reserve rivers, concentrations of Escherichia coli, cadmium, lead, iron, manganese, and ammonium exceeded guideline levels under a severe drought and a dispersal of cyanobacteria appeared under a high-flow pulse in La Niña year. The ammonium concentration exceeded the level for human drink with the overbanking flood stage in El Niño year. These occasional detections pose a potential risk to the aquatic life and, especially, to the inhabitants of the Reserve. Flow duration curves, IHA, and EFC are useful tools to evaluate trends or changes of ecological and social relevance in flow regime characteristics.

Integrating ecosystem-service tradeoffs into environmental flows decisions for Baiyangdian Lake

Environmental flows play an important role in sustaining or enhancing the ecosystem services provided by wetlands. In this study, we quantified ecosystem services values and used the results to design an environmental flows regime for Baiyangdian Lake, the largest shallow freshwater lake in northern China. To do so, we proposed explicit tradeoffs among ecosystem services. We used emergy analysis to value the lake's ecosystem services from 1980 to 2011. We found that the regulating services contributed most to the total ecosystem services value from 1980 to 1989, followed by provisioning and cultural services; after 1990, the contribution of provisioning services became far greater than those of the other two services, followed by regulating services until 1998 and cultural services thereafter. We examined the relationships among the ecosystem services and environmental flow regimes, and found that regulating was strongly related and provisioning was moderately strongly related to all of the environmental flow components except for inflows; in contrast, cultural services were only weakly related to these components except for drought duration. Furthermore, we divided the study period's environmental flow regimes into four scenarios (high, intermediate, low, and extremely low flow regimes), which correspond to different environmental flow management strategies. Under the four scenarios, tradeoffs existed between all pairs of services. However, the intermediate flow regime provided the best overall tradeoff among the three services, and is therefore the recommended environmental flows regime. This form of analysis can therefore guide local environmental flows decisions that involve tradeoffs between different management objectives.

Comparing flow regime, channel hydraulics, and biological communities to infer flow–ecology relationships in the Mara River of Kenya and Tanzania

Equatorial rivers of East Africa exhibit unusually complex seasonal and inter-annual flow regimes, and aquatic and adjacent terrestrial organisms have adapted to cope with this flow variability. This study examined the annual flow regime over the past 40 years for three gauging stations on the Mara River in Kenya and Tanzania, which is of international importance because it is the only perennial river traversing the Mara-Serengeti ecoregion. Select environmental flow components were quantified and converted to ecologically relevant hydraulic variables. Vegetation, macroinvertebrates, and fish were collected and identified at target study sites during low and high flows. The results were compared with available knowledge of the life histories and flow sensitivities of the riverine communities to infer flow–ecology relationships. Management implications are discussed, including the need to preserve a dynamic environmental flow regime to protect ecosystems in the region. The results for the Mara may serve as a useful model for river basins of the wider equatorial East Africa region.Editor Z.W. Kundzewicz; Guest editor M. AcremanCitation McClain, M.E., Subalusky, A.L., Anderson, E.P., Dessu, S.B., Melesse, A.M., Ndomba, P.M., Mtamba, J.O.D., Tamatamah, R.A., and Mligo, C., 2014. Comparing flow regime, channel hydraulics and biological communities to infer flow–ecology relationships in the Mara River of Kenya and Tanzania. Hydrological Sciences Journal, 59 (3–4), 801–819.

EFCAM: A METHOD FOR ASSESSING ALTERATION OF ENVIRONMENTAL FLOW COMPONENTS

ABSTRACTThe environmental flow components (EFCs) are a set of 34 streamflow statistics computed by the Indicators of Hydrologic Alteration software, which are used for environmental flow assessments and developing environmental flow recommendations. The objective of this paper is to demonstrate a methodology for analysing and summarizing the alteration of EFCs, called the EFC assessment method (EFCAM). EFCAM uses non‐parametric rank‐sum statistical tests, sometimes in conjunction with per cent change, to produce ratings of alteration for each EFC statistic, for both central tendency and range of variability. These ratings are combined into summary indexes of alteration, by event type (extreme low flow, low flow, high‐flow pulse, small flood and large flood), flow characteristic (frequency, magnitude, duration, timing and rise/fall rates) and overall. EFCAM is demonstrated by analyzing typical patterns of EFC changes in 66 rivers across the United States where flow is altered by dams. The results reported here show that EFCAM is an effective method for efficiently summarizing flow alteration of ecologically relevant components of flows, and hence would be a useful addition to the Indicators of Hydrologic Alteration software. Results of this study show an overall trend towards compression of the hydrograph from above and below into a more limited overall range on these 66 rivers. The results shown here add to previous findings on dam impacts on river flows by separating out alteration in different segments of the hydrograph, and identify some patterns of alteration not previously reported. Although the version of EFCAM used here is believed to be appropriate for most situations, it is flexible and can be tailored to the needs of a particular project by including or excluding certain flow statistics or using a different weighting system. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Braided River Flow and Invasive Vegetation Dynamics in the Southern Alps, New Zealand

In mountain braided rivers, extreme flow variability, floods and high flow pulses are fundamental elements of natural flow regimes and drivers of floodplain processes, understanding of which is essential for management and restoration. This study evaluated flow dynamics and invasive vegetation characteristics and changes in the Ahuriri River, a free-flowing braided, gravel-bed river in the Southern Alps of New Zealand's South Island. Sixty-seven flow metrics based on indicators of hydrologic alteration and environmental flow components (extreme low flows, low flows, high flow pulses, small floods and large floods) were analyzed using a 48-year flow record. Changes in the areal cover of floodplain and invasive vegetation classes and patch characteristics over 20years (1991-2011) were quantified using five sets of aerial photographs, and the correlation between flow metrics and cover changes were evaluated. The river exhibits considerable hydrologic variability characteristic of mountain braided rivers, with large variation in floods and other flow regime metrics. The flow regime, including flood and high flow pulses, has variable effects on floodplain invasive vegetation, and creates dynamic patch mosaics that demonstrate the concepts of a shifting mosaic steady state and biogeomorphic succession. As much as 25% of the vegetation cover was removed by the largest flood on record (570m(3)/s, ~50-year return period), with preferential removal of lupin and less removal of willow. However, most of the vegetation regenerated and spread relatively quickly after floods. Some flow metrics analyzed were highly correlated with vegetation cover, and key metrics included the peak magnitude of the largest flood, flood frequency, and time since the last flood in the interval between photos. These metrics provided a simple multiple regression model of invasive vegetation cover in the aerial photos evaluated. Our analysis of relationships among flow regimes and invasive vegetation cover has implications for braided rivers impacted by hydroelectric power production, where increases in invasive vegetation cover are typically greater than in unimpacted rivers.

Environmental Flow Components for Measuring Hydrologic Model Fit during Low Flow Events

AbstractThe indicators of hydrologic alteration (IHA) is a statistical flow methodology for characterizing ecologically important streamflows. Typically, IHA has been used to identify the extent of human effects on a stream’s hydrology and to set management goals to restore the stream ecology. In this work, the use of the seven “extreme low flow” statistics of the IHA is extended to the evaluation of the performance of a hydrologic simulation model under low flow conditions. Specifically, this work uses the IHA framework to evaluate the accuracy of the Chesapeake Bay Program Phase 5 (CBP5) watershed model during low flow events on a regional scale that is relevant to many water supply planners and managers. Because the CBP5 model’s primary focus is predicting the Bay’s water quality, the measures used to calibrate the CBP5 model focused primarily on the calibration of the entire hydrological record and had only a secondary emphasis on specific flow regimes, such as low flows and very low flows, although t...

HYDROLOGIC MODIFICATION FROM HYDROELECTRIC POWER OPERATIONS IN A MOUNTAIN BASIN

ABSTRACTThe natural flow paradigm suggests that components of the natural streamflow regime and variability should be managed to maintain important ecosystem functions and services. Mountain rivers can exhibit extreme flow variability and provide critical aquatic habitat and ecosystem services but can be severely impacted by hydroelectric power (HEP) development and operations that will likely increase in the future. The hydrologic modification from HEP operations in the Upper San Joaquin River Basin, California, was evaluated across 15 river and stream locations throughout the basin. Flow modifications in Bear Creek, an otherwise unimpacted high‐elevation subbasin, were evaluated in detail using a number of hydrologic metrics, including Indicators of Hydrologic Alteration (IHA), environmental flow components of IHA, flow duration curves, ecodeficit and comparisons using equivalence testing. The uncertainty of the metrics based on confidence intervals was also evaluated for unimpaired (upstream) and existing (impaired or downstream) conditions. Results showed that metrics for median values changed considerably for most locations under impaired conditions, but the direction and extent of change varied depending on the location and flow metric. Metrics for variability (coefficients of dispersion) changed even more. Most metrics showed that flow modifications in Bear Creek were substantial, including decreases in high flows and increases in most low‐flow metrics. However, some flow variability metrics increased because of large flood flows during several years overwhelming and bypassing the dam/diversion structure. Uncertainty in metrics varied considerably throughout the basin but generally increased for impaired conditions. Uncertainty should be explicitly considered when evaluating hydrologic modification from HEP in mountain watersheds. A number of metrics should be used depending on objectives and spatial scale, including a subset of key IHA metrics across multiple sites and other methods to provide detailed information on flow modification in conjunction with other environmental flow assessment techniques at key locations. Copyright © 2011 John Wiley &amp; Sons, Ltd.

A Database and Meta-Analysis of Ecological Responses to Stream Flow in the South Atlantic Region

Generalized and quantitative relationships between flow and ecology are pivotal to developing environmental flow standards based on socially acceptable ecological conditions. Informing management at regional scales requires compiling sufficient hydrologic and ecological sources of information, identifying information gaps, and creating a framework for hypothesis development and testing. We compiled studies of empirical and theoretical relationships between flow and ecology in the South Atlantic region (SAR) of the United States to evaluate their utility for the development of environmental flow standards. Using database searches, internet searches, and agency contacts, we gathered 186 sources of information that provided a qualitative or quantitative relationship between flow and ecology within states encompassing the SAR. A total of 109 of the 186 sources had sufficient information to support quantitative analyses. Ecological responses to natural changes in flow magnitude, frequency, and duration were highly variable regardless of the direction and magnitude of changes in flow. In contrast, the majority of ecological responses to anthropogenic-induced flow alterations were negative. Fish abundance, diversity, reproduction, and habitat consistently showed negative responses to anthropogenic flow alterations, whereas other ecological categories (e.g., macroinvertebrates and riparian vegetation) showed somewhat variable responses and even positive responses (e.g., algal abundance). Fish and organic matter had sufficient sample sizes to stratify natural flow-ecology relationships by specific flow categories (e.g., high flow, baseflows) or by physiographic province (e.g., Coastal Plain, Piedmont). After stratifying relationships, we found that significant correlations existed between changes in natural flow and fish responses. In addition, a regression tree explained 57% of the variation in fish responses to anthropogenic and natural changes in flow. Altogether, our results suggested that the source of flow change and the ecological category of interest played primary roles in determining the direction and magnitude of ecological responses. Furthermore, our results suggest that developing broadly generalized relationships between ecology and changes in flow at a regional scale is unlikely unless relationships are placed within meaningful contexts, such as environmental flow components or geomorphic settings.

Design of a naturalized flow regime—an example from the Lower Missouri River, USA

AbstractA group of river managers, stakeholders, and scientists met during summer 2005 to design a more naturalized flow regime for the Lower Missouri River (LMOR). The objective was to comply with requirements under the U.S. Endangered Species Act to support reproduction and survival of threatened and endangered species, with emphasis on the endangered pallid sturgeon (Scaphirhynchus albus), while minimizing negative effects to existing social and economic benefits of prevailing river management. Specific hydrograph requirements for pallid sturgeon reproduction are unknown, hence much of the design process was based on features of the natural flow regime. Environmental flow components (EFCs) extracted from the reference natural flow regime were used to design and assess performance of alternative flow regimes.The design process incorporated a primary stage in which conceptual hydrographs were developed and assessed for their general ecological and social‐economic performance. The second stage accounted for hydroclimatic variation by coding the conceptual hydrographs into reservoir release rules, adding constraints for downstream flooding and low‐storage precludes, and running the rules through 100 years of hydroclimatic simulation. The output flow regimes were then evaluated for presumed ecological benefits based on how closely they resembled EFCs in the reference natural flow regime. Flow regimes also were assessed for social‐economic cost indicators, including days of flooding of low‐lying agricultural land, days over flood stage, and storage levels in system reservoirs.Our experience with flow‐regime design on the LMOR underscored the lack of confidence the stakeholders place in the value of the natural flow regime as a measure of ecosystem benefit in the absence of fundamental scientific documentation. Stakeholders desired proof of ecological benefits commensurate with the certainty of economic losses. We also gained insight into the processes of integrating science into a collaborative management exercise. Although the 2005 collaborative effort failed to reach a consensus among stakeholders on a naturalized flow regime, the process was successful in pilot‐testing a design approach; it helped focus scienctific efforts on key knowledge gaps; and it demonstrated the potential for collaborations among scientists, stakeholders, and managers in river management decision making. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Application of the Indicators of Hydrologic Alteration Software in Environmental Flow Setting1

Abstract: River scientists are increasingly asked to provide recommendations about the amount and timing of water flows needed to support ecosystem health. The need for scientifically credible environmental flow assessments and the limited availability of resources to conduct in‐depth studies place a premium on methods that can be readily applied at low cost. The Indicators of Hydrologic Alteration (IHA) software program was originally developed by The Nature Conservancy in the 1990s to quickly process daily hydrologic records to enable characterization of natural water conditions and facilitate evaluations of human‐induced changes to flow regimes. The evolution of the IHA software is discussed, including recent revisions and additions to the IHA that have improved its utility in environmental flow‐setting processes. Drawing from holistic methodologies developed around the world, the ability to calculate characteristics of five components of flow important to river ecosystem health – extreme low flows, low flows, high‐flow pulses, small floods and large floods – has been added to the IHA. A practical advantage of these environmental flow components is that an environmental flow prescription based upon them can be readily implemented in most water management settings. Frequently used as a one‐time generator of flow statistics, the value of the IHA increases when used interactively with ecological models. A process for linking IHA output to an ecological model to explore flow‐ecology relationships within an adaptive management context is presented and demonstrated through its application on the Green River, Washington. The IHA used in conjunction with ecological models facilitates the creation and testing of flow‐ecology hypotheses, formulation of water and land protection or restoration goals, and development of a focused research and monitoring program, all important components of environmental flow‐setting processes.